1. Technical Field
The present invention relates to a power generation system which employs fuel cells having electrolytes of molten carbonate, and more particularly it relates to a power generation system which includes stacks of fuel cells and reforming devices for reforming fuel gas to anode gas.
2. Background Art
The principle of the fuel cell is the reverse reaction of the electrolysis of water, i.e., chemical reaction of hydrogen of the anode gas with oxygen of the cathode gas accompanies production of electricity and water. A power generation system with use of fuel cells generally consists of a stack of fuel cell elements, a reformer for reforming the natural gas to the anode gas with steam, and a heat exchanger. Each cell element includes a porous anode electrode, a porous cathode electrode, and an electrolyte plate sandwiched by the anode and the cathode electrodes. The anode gas passages and the cathode gas passages are respectively defined on both faces of the separator plates. The fuel gas such as natural gas is supplied with steam to a reforming chamber of the fuel gas reforming device so as to reform the fuel gas to hydrogen-rich anode gas. The anode gas so obtained is then supplied to the anode gas passage formed on one face of the separator plate. On the other hand, an exhaust gas from the anode gas passage and fresh air heat the reforming chamber so as to maintain the reforming temperature. After that, the exhaust gas is mixed with air and then supplied to the cathode gas passage as the cathode gas. As for electrolyte plates, various types are available; for example, one made of phosphoric acid and another made of molten carbonate are well known. Reactions at the anode and the cathode electrodes, where the molten carbonate is employed as the electrolyte, are given by following equations: EQU Cathode: 1/2 0.sub.2 +C0.sub.2 +2e.sup.- ----CO.sub.3.sup.2- EQU Anode: H.sub.2 +CO.sub.3.sup.2- ----H.sub.2 O +CO.sub.2 +2e.sup.-
On the other hand, reforming reactions are as follows: EQU CH.sub.4 +H.sub.2 O ----C0+3H.sub.2 EQU CO+H.sub.2 O ----CO.sub.2 +H.sub.2
In the conventional fuel cell type power generation system, the fuel cell stack and the reformer have been designed as small as possible, namely they have plate-type configuration. However, since external conduits and piping for supplying/discharging the anode and cathode gases to/from the fuel cell stack and the reformer have been intricate, the entire system cannot be designed compact.